Process of producing pure zinc sulfid and thiosulfates.



PIERRE PIPEREAUT AND ANTONY VILA, 0F PARIS, FRANCE.

PROCESS OF PRODUCING PURE ZINC SULFID AND TI-IIOSULFATES.

No Drawing.

Specification of Letters Patent.

Application filed September 15, 1908.

Patented J an. 2, 1912.

Serial No. 453,179.

" To all whom it may concern:

Be it known that we, PIERRE PIPEREAUT and ANTONY VILA, chemicalengineers, citizens of the Republic of France, residing at 13 Avenue desGobelins, Paris, in the Department of Seine, in the Republic of France,have invented certain new and us ful Improvements in Processes ofProducing Pure Zinc Sulfid and Thiosulfates, for which we have obtaineda patent in Belgium, No.

202,686, dated September 19, 1907, and applied for a patent in Germany,dated November 29, 1907; and we do hereby declare the following to be afull, clear, and, exact description of the invention, such as willenable others skilled in the art to which it appertains to make and usethe same.

This invention relates to an improved process for preparing zinc sulfidand alkali thiosulfates.

It is old to produce zinc sulfid by causing alkaline sulfids tolixiviate with alkaline solution of zinc. The zinc sulfid obtained bythis method is ery bulky, and is in a sort of collodial form; it can .befiltered only with great difliculty, and cannot be washed easily.

We have found that in the case of zinc, it

is suflicient to take ores of zinc, blende, calamin, smithsonite, BrokenHill ore, Greensbit ore, etc., and roast them in order to obtain an oxidor roasted product and to subject them to the action of a causticalkaline lye such as soda. The decanted clear solution is then boiled,and then pulverized sulfur is added to it in the required quantity andsuf' ficient to convert all metals dissolved, except that which isdesired to recover, into insoluble sulfids, which are first precipitatedas impurities. After the separation of these impurities, to the solutionis then added, in small amounts, sufficient sulfur to convert the metalremaining in solution-into sulfid. Alkaline sulfid in nascent state isthereby produced.

This process difi'ers entirely from the action of alkaline sulfids,previously manufactured, on alkaline solutions of metals.

In the process according to this invention, the precipitation is not animmediate one, it is the result of a series of progressivetransformations terminating finally in the production of the sulfiddesired, moreover, it is completed only after long boiling. On thecontrary, when the same-solutions are precipitated by means of analkaline sulfid prepared in advance, it is well known that in suchconditions the precipitation is immediate and complete. It has beenfound that zinc sulfid can be obtained in an easily filterable granularstate, if one does not heat the alkaline solutions of zinc with alreadyformed, alkaline sulfide, but if one heats these alkaline solutions ofzinc, with the sulfur under the conditions described the al ka-' linesulfid in a nascent state, reacts with the zincates.

This process is applicable to carbonates and compounds of other metalsof the zinc group. The compound of ;metal and-al kali reacts then onthenascentfsulfid, and

the reaction once having eh started, continues gradually, as in the caseof zinc.

The precipitates obtained by this process are in the form of microscopicgrains of great density, the Washing and drying operations become veryeasy, so that it is possible to obtain pure products of unctuousnessequal to that of talc, in all 'cases in which the ordinary processesgive merely gelatinous collodial precipitates which it is impossible towash completely.

. Alkaline liquids used for the transformation of oxids of oresintometallic sulfids, can be utilized a great number of'times, until thecontents of alkaline thiosulfate which is formed as a by-product'owingto the long contact with the air becomes so great that it is advisableto eifcct its crystallization.

If we are examining the example given for zinc sulfid, we find the wellknown equations It is Well known that if sulfur is added to a pureboiling alkaline liquor, there are hydrated sulfids formed after thequantities taking part in the reaction: Na S,9H O (KircherAnnaZ der Ph.t. XXXl, p. 339). Na,S,5H O and Na S ,5I-I O ('Bottger- Arm, 0h. Pkg s.Liebig223, 535-1884). Na,S .6H O (Schone, Ann. Ph. 0h. Pogg.

.131", 386-1867).' Na S and Na S, (Bloxa. J. Chem. Sec. 77, 7531900).There is also sodium thiosulfate formed S O Na ,5H O.

If these hydrated sulfids are added by themselves to a solution ofalkaline zincate, there is immediately formed a precipitate of Z1110sulfid.

I In the operation described, the sulfur is introduced' into the boilingalkaline s0lu-' boiling liquid looses slowly its yellow color vandproduces a fine white powder.

advisable to replace a small fraction of the and is quite colorless whenthe reaction is finished.

- The following equation is given by way of example:

This compound, in contact with ZnO Na w1ll soon dissociate and give:

(nascent) We use for a quantity of 100 kgs. of molten ore, containingabout 30 kgs. of metallic zinc, 80 kgs. ofcaustic soda diluted in 60liters of water; the whole is heated in an apparatus of iron plate, orother iron apparatus. We heat to ebullition for 6 hours at 130-1et0 C.;after cooling we add water to form 100 liters of solution. After 12hours, 90 liters of clear liquid can be decanted. To this liquor, whileboiling we add a small quantity of pulverized sulfur after 3 hoursboiling the colored sulfids are precipitated, they are separated; and tothe decanted and purified liquor, we add 10 kgs. of pulverized sulfur,and we boil throughout 4 hours to finish the reaction. The zinc sulfidobtained by this method is washed and dried It is alkaline lye aftereach operation.

The operation is carried out in the following way: A solution of zinc,oxid in caustic alkali, for instance, NaOH, is made at first; thissolution is kept boiling and the quantity of sulfur'necessary to formzinc sulfid is added while boiling. At first, the

sulfur dissolves without glving any pre cipitate; after a certain timeof heating there is found a granular zinc sulfid pre cipitate, whichsettles very well to the bot tom and can easily be filtered and washed.Instead of Zinc oXid dissolved in alkali one can use also a solution ofzinc carbonate in caustic alkali solutions.

Instead of zinc oxid or carbonate, cadmium oxid, carbonate or acetatemay be employed in order to obtain in the same manner cadmium sulfid.Alkaline liquid used for the transformation of oxids or ores intounctuous sulfids, can be utilized a great number of times, until thecontents of alkaline thiosulfate which is formed as a byproduct, owingto the long contact with the air, become so greatthat it is advisable toeffect its crystallizations.

We claim: i

1. The process for treating zinc sulfid ore to recover zinc sulfid ina'granular form,

which consists in lixiviating the ore with caustic alkali solutionthereby forming alkali zincate, heating to boiling, adding sufficientfree sulfur to precipitate the metals other than zinc, in the form ofsulfids, and separating the same from the solution prior to theprecipitation of the zinc sulfid and then adding, in small amounts,sufficient free sulfur to precipitate the zinc present,

while keeping the liquid hot.

2. The process for treating zinc sulfid ore to recover zinc sulfid in agranular form, which consists in lixiviating the ore with caustic alkalisolutionthereby forming alkali zincate, heating to boiling, addingsufficient free sulfur to precipitate the metals other than zinc, in theform of sulfide, separating the same from the solution prior to theprecipitation of the zinc sulfid and then adding, in small amounts,suflicient free sulfur to precipitate the zinc present while keeping theliquid hot, and filtering to remove the zinc sulfid. I

In testimony whereof we our signatures.

' PIERRE PIPEREAUT.

ANTONY VILA. In the presence of-- THEODORE REDIG, HERMANN LUTHER.

